GB2282439A

GB2282439A - Reflector for a vehicular lamp

Info

Publication number: GB2282439A
Application number: GB9418723A
Authority: GB
Inventors: Kazushi Yoshida
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 1993-10-01
Filing date: 1994-09-16
Publication date: 1995-04-05
Anticipated expiration: 2014-09-16
Also published as: GB2282439B; DE4435207A1; JPH07105704A; JP3207031B2; GB9418723D0

Description

-0 1 REFLECTOR FOR A VEHICULAR LAMP 2282439 The present invention relates

to a ref lector for a vehicular lamp by which a light distribution pattern diffused in the horizontal direction can be obtained without depending upon the light distribution control function of lens steps, and also a luminous intensity distribution can be realised in which the luminous intensity is gently changed from the centre of the light distribution pattern to the periphery.

With the demand for the aerodynamic characteristics in automobile design, it is necessary to design a head lamp corresponding to what is called a slant nose at which the front portion of an automobile body is made narrower.

Therefore, it is desired to provide a reflector in the front of which a plain lens is placed in which lens steps do not need to be f ormed, or alternatively it is desired to provide a reflector in the front of which an approximately plain lens is placed.

As an example of the above reflector, US-A-1,898,167 discloses a reflector in which parabolas of different focal distances are established on horizontal and vertical surfaces including the optical axis of a reflector. When a parabola of a short f ocal distance on the vertical surface is moved along a parabola of a long focal distance on the horizontal surface, the reflecting surface is formed.

In Japanese Post-examined Patent Publication No. Show. 59-53641, the present applicant discloses a reflector having a configuration by which broad dif fusion can be easily provided in the horizontal direction. Its ref lecting surf ace is f ormed in such a manner that the reference curve on a horizontal section including the reference axis is expressed by an expression in which a high-order term is added to the expression of a parabola. In this case, the expression is described as follows:

y 2 = 4 - f. x + a. xn 2 where f is a focal distance a and n are constants, with a > 0 and n > 1.

Then, the reflecting surface is formed as an enveloping surface of a group of rotational parabolic surfaces contacting with this at a point on the reference curve and at the same time the rotational parabolic surfaces have the same focus as that of the reference curve.

However, in the reflector described above, the following problem may be encountered with respect to the luminous intensity distribution in the light distribution pattern.

In the light distribution pattern of a vehicular lamp, it is essential to provide a light distribution pattern in which the pattern is greatly diffused in the horizontal direction compared with the vertical direction. In a cornering lamp, front turn signal lamp and stop lamp, the lamp is required to be formed into a rectangle which is horizontally elongate, and further the luminous intensity distribution is required to gently decrease from the center to the periphery. However, in the former reflector disclosed in US-A-1,898,167, a parabola is adopted as a fundamental curve. Therefore, in the luminous intensity distribution of the light distribution pattern provided by this reflector, a relative difference of luminous intensity between the center and the periphery is increased. Accordingly, in order to compensate the insufficient diffusion of luminous intensity, the dependability upon light distribution control function of the lens steps formed on front lens is increased. In the latter reflector, i.e., Japanese Post-examined Patent Publication No. Show. 59-53641, when a point light source is placed at the focus, the obtained light distribution pattern is formed approximately lozenge-shaped, so that a portion directed to the periphery in the horizontal direction is made narrower. Therefore, the relative difference of luminous intensity between the center of the light 3 distribution pattern and the periphery in the horizontal direction becomes remarkable.

The present invention was made in view of the foregoing difficulties accompanying the conventional reflector. That is, an object of the invention is to provide a reflector for a vehicular lamp capable of controlling a luminous intensity distribution independently in the horizontal or vertical direction.

Another object of the invention is to provide a reflector for a vehicular lamp in which the light distribution control is conducted without the help of the lens steps of the f ront lens, so that an extreme dif f erence of the luminous intensity is not caused between the center and the periphery of the light distribution pattern.

According to the present invention there is provided a ref lector f or a vehicular lamp capable of f orming a light distribution pattern diffused in the horizontal direction, wherein a reference curve established on a horizontal surface including a reference axis and a reference curve established on a vertical surface including the reference axis are expressed by the following expression:

x= (h 2 /r) / (1 +1 - (1 +M. (h/r) 2) +AM (h') where 11x11 is a coordinate established on the respective reference axis, "h" is a coordinate established on an axis perpendicular to the x axis on a horizontal or vertical surf ace including the x axis, Ilrll and 'W' are constants, and ",&M (h n), is a correction term, which is a polynomial of the n-th order of a positive coefficient relating to "h", wherein 'In" is an even number not less than 4; and a reflecting surface is formed when one reference curve is moved so that the plane in which the moved curve exists remains parallel to the plane in its starting position throughout the movement along the other reference curve so that the reference axis of one curve is located on a 4 horizontal or vertical surface including the reference axis of the other reference curve.

The reference curves of the second order are deformed by establishing the number of order of the correction term added to the curves of the second order. At the same time, when one of the reference curves is moved along the other reference curve so that the reference axes are parallel with each other, a reflecting surface is formed as a group of curves. In this way, the luminous intensity distribution can be independently controlled in the horizontal and vertical directions so that an extreme difference of luminous intensity is not caused between the center of the light distribution pattern and the periphery.

In the accompanying drawings:

Fig. 1 is a view showing an example of the reference curve on the horizontal axis with respect to the reflection surface of the reflector according to the present invention, wherein Fig. 1A is a view showing an outline of the profile of a curve, and Fig. 1B is a view in which the curves surrounded by the circle shown in Fig. 1A are enlarged; Fig. 2 is a perspective view for explaining a reflecting surface formed when the reference curve on the vertical surface is moved in parallel along the reference curve on the horizontal surface; Fig. 3 is a perspective view for explaining a reflecting surface formed when the reference curve on the horizontal surface is moved in parallel along the reference curve on the vertical surface; Fig. 4 is a schematic illustration showing a projection pattern of the reflector according to the present invention and also showing luminous intensity distributions in the horizontal and vertical directions; Fig. 5 is a view showing together with Figs. 6 to 9 an example of the vehicular lamp in which the reflector of the present invention is used, and Fig. 5 is a horizontal sectional view; X Fig. 6 is a longitudinally sectional view; Fig. 7 is a front view of the reflector; Fig. 8 is a schematic illustration showing a relation between the reference axis of the reflecting region composing the reflecting surface and the primary optical axis of the reflecting surface; and Fig. 9 is a schematic illustration showing a light distribution pattern of the reflector.

Figs. 1A and 1B are views showing a reference curve 1 established on a horizontal section including the reference axis. A rectangular coordinate is established in which the reference axis is determined to be the x axis, and an axis on the horizontal surface perpendicular to the x axis is determined to be the y axis. The reference curve 1 can be expressed by the following expression provided when a correction term of a polynomial is added to an expression of a curve of the second order.

[EXPRESSION 1] 2 X = T +,E An.yn nz4 1+ 1-(1,.K).(.Z)2 r In this connection, in the above expression, 11r11 is a paraxial radius of curvature, "K" is a conical constant, and A, (n is an even number not less than 4) is a positive coefficient by which the n-th term is multiplied.

When the terms not less than fourth order are neglected, "Expression 111 results in an expression of a curve of the secondary order. For example, when K = -1, the expression expresses a parabola, the focal distance of which is r/2, and when K > -1, the expression expresses an ellipse.

For the purpose of making a comparison with the reference curve 1, a parabola 2 indicated by a broken line is also shown in Fig. 1. As clearly can be seen from the positive coefficient An of the correction term, the 6 reference curve 1 is closer to the x axis than the parabola 2 is.

The curves 3 and 4 shown in Fig. 1 express the effect of a correction term for the curve of the second order. The curve 3 expresses a curve in which only a correction term of the fourth order is added to an expression of the curve of the second order. The curve 4 expresses a curve in which only a correction term of the sixth order is added to an expression of the curve of the second order.

A correction term of which the number n of order is small affects a profile of the paraxial portion of the x axis of the reference curve 1, and a correction term of which the number n of order is large affects a profile of the portion separated from the x axis of the reference curve 1.

In the same manner, a reference curve established on the vertical section including the reference axis is expressed by an expression in which a correction term of the polynomial is added to an expression of the curve of 20 the second order.

In the case where a rectangular coordinate is established in which the reference axis is defined as the x axis and an axis on the vertical surface perpendicular to the x axis is def ined as the z axis, the ref erence curve is expressed by the following expression.

[EXPRESSION 2] z 2 X = X +E Bn Zn 1+ 1-(j+K).( Z)2 n2A r In this connection, in the above expression, llrll is a paraxial radius of curvature, 'W' is a conical constant, and B,, (n is an even number not less than 4) is a positive coefficient by which the n-th term is multiplied.

As illustrated in Fig. 2, a reflecting surface is formed when the reference curve 5 established on the 7 vertical section including the reference axis is moved in parallel in the horizontal direction along the aforementioned reference curve 1.

That is, the ref lecting surf ace 6 is f ormed in the following manner. The ref erence curve 5 is moved in the horizontal direction along the reference curve 1 so that the apex P of the reference curve 5 can be located on the reference curve 1 at all times and also the reference axis of the reference curve 5 can be parallel with the reference axis of the reference curve 1. When the above operation is performed, the reflecting surface 6 is formed as a curved surface.

Either the reference curve 1 or the reference curve 5 may be relatively moved with respect to each other. As illustrated in Fig. 3, the reference curve 1 may be moved along the reference curve 5 in the vertical direction so that the apex Q of the reference curve 1 can be located on the reference curve 5 at all times and also the reference axis of the reference curve 1 can be parallel with the reference axis of the reference curve 5.

A left upper view of Fig. 4 expresses a pattern 7 projected on the front screen by the reflecting surface 6 in the case where a point light source is located at a f ocus relating to the term of the curve of the second order of the reference curve 1. In the drawing, "H - H" is a horiiontal line, and "V - V' is a vertical line.

The projection pattern 7 is approximately formed into a rectangle that is long from side to side. Concerning the luminous intensity, the brightness is high at the center, and the brightness tends to be gradually reduced in the periphery. When the number of order of the correction term is made different between the reference curves 1 and 5, the degree of reduction of the luminous intensity can be changed between the luminous intensity distribution in the horizontal direction and that in the vertical direction.

The higher the number of order of the correction term of the reference curve 1 or 5 is, the more the profile of 8 the periphery of the ref erence curve is deformed to the reference axis side from the curve of the second order. Consequently, from the viewpoint of optics, it is possible to reflect the light from the periphery of the reflector across the reference axis and to utilize it for the formation of the center of luminous intensity in the projection pattern.

For example, when the correction term is A4- y 4 + A8- y 8 in "Expression ill showing the reference curve 1, and also when the correction term is B. z 4 + B6 Z 6 in "Expression 211 showing the reference curve 2, the degree of reduction of luminous intensity from the center of the projection pattern to the periphery is more increased in the horizontal direction than in the vertical direction.

These circumstances are schematically shown in the luminous intensity distribution diagram located on the right of the projection pattern 7 in Fig. 4 and also shown in the luminous intensity distribution diagram located under the projection pattern 7. The view located under the projection pattern 7 is a luminous intensity diagram in the horizontal direction, and the view located on the right of the projection pattern 7 is a luminous intensity diagram in the vertical direction. In both diagrams, the L axis represents the luminous intensity.

In order to relatively gently reduce the luminous intensity from the center to the periphery as shown in the diagrams, a term of the low order may be used f or the correction term, and also a term of the high order may be used for the correction term so as to realize a luminous intensity distribution in which a relatively large difference of gradation is made between the center and the periphery. In this connection, the correction term of high order and that of low order should be chosen in accordance with the required luminous intensity distribution. That is, the correction term of high order and that of low order should be individually chosen for each different type of 9 reflector without reference uniformly to a specific number of order.

Figs. 5 to 7 are views showing an example of the vehicular lamp to which the reflector of the present invention is applied. This is an example in which the present invention is applied to a reflecting section of the front turn signal lamp.

The lamp apparatus 8 includes: a lamp body 9 of which the front is open; a front lens 10 located so that the front lens 10 covers a front opening of the lamp body 9; and an electric bulb 11, the light emitting section of which is located at a predetermined position in the lamp body 9.

When an inside of the lamp body 9 on the back end side is subjected to reflecting processing, a reflecting surface is formed, so that this portion is used for the reflecting section 12. In this connection, instead of forming a reflecting surface inside the lamp body 9, a reflector different from the lamp body 9 may be provided in it.

Numeral 13 is a back end wall Protruding backward from the back end surf ace of the lamp body 9. A mounting member 14 for the electric bulb 11 is fixed to the back end wall.

A glass bulb section 15 of the electric bulb 11 is disposed at a predetermined position in the lamp body 9 through a circular hole 12a formed in the reflecting section 12. The glass bulb section 15 is detachably supported by the mounting member 14 through a flange 16a provided in a base section 16 and also supported by engaging sections 16b, 16b, --- provided in front of the flange 16a.

Numeral 17 is a coil-shaped filament, and the central axis is disposed so that it extends in the horizontal direction.

Numerals 18, 19 are side walls of the lamp body 9.

The left side wall 18 is extends forwards from a front end of the reflecting section 12. The right side wall 19 extends backwards from a front end of the reflecting section 12. A lens mount 20 for mounting the front lens 10 is formed at the outer edge portions of the side walls 18, 19.

A lens section 21 of the front lens 10 is curved into a prof ile which is the same as the curved prof ile of a front nose of the vehicle body (shown by a two-dotted chain line in Figs. 5 and 6). The lens section 21 is a plain lens in which no lens steps are f ormed. Alternatively, the lens section 21 is a lens approximately the same as a plain lens. A backwardly protruding peripheral wall 22 is formed in the outer periphery of the lens section 21 integrally with the lens section 21. A backwardly protruding mounting protrusion 23 is formed at an edge of the peripheral wall 22 on a side opposite to the lens section 21. Under the condition that this mounting protrusion 23 is received in a groove 20a of the lens mounting section 20 of the lamp body 9, for example, by screws.

Numeral 24 is an inner cap covering the glass bulb section 15 of the electric bulb 11. This inner cap is provided for forming a coloured light source together with the electric bulb 11. Fig. 7 shows a front view of the reflecting section 12. With respect to the light distributing control, the reflecting surface of the reflecting section 12 is divided into 4 reflecting sections 25, 26, 27, 28. The reflecting regions 25, 26 occupy the most portion of the reflecting surface. Both reflecting regions 25 and 26 are designed by the same method as that of the aforementioned reflecting surface 6. 30 When a view is taken f rom the f ront, the ref lecting region 25 is located on the left of a vertical surface including the primary optical axis of the reflecting section 12 (the primary optical axis is an axis passing at the center of the circular hole 12a in a direction perpendicular to the surface of Fig. 7). The reflecting region 26 is located on the right of the vertical surface f 11 including the primary optical axis of the reflecting section 12.

As illustrated in Fig. 8, the reference axes of the reflecting regions 25, 26 are inclined with respect to the primary optical axis of the reflecting section 12.

In the drawing, 11L - L" denotes the primary optical axis of the reflecting section 12. The reference axis of the reflecting region 25 denoted by 1IL25 - L2511 is inclined on the horizontal surface including the axis L - L by a predetermined angle with respect to the axis L - L.

In the same manner, in the reflecting region 26, the reference axis denoted by 1IL26 - L2611 is inclined on the horizontal surface including the axis L - L by a predetermined angle with respect to the axis L - L.

When the reference axes of the reflecting regions 25, 26 are inclined with respect to the axis L - L, the luminous intensity at the center of the light distribution pattern is suppressed so that it can not be unnecessarily increased.

As shown in Fig. 7, the remaining reflecting regions 27, 28 are respectively located at the left upper corner and the left lower corner of the reflecting region 25.

Both profiles of these reflecting regions are formed into a rotational elliptic surface.

Fig. 9 shows an approximately cross-shaped light distribution pattern 29 obtained by the lamp apparatus 8 for vehicle use. In the drawing, the luminous intensity distribution is schematically expressed by the isocandela lines.

The reflecting patterns 25,26 mainly contribute to the formation of the rectangular portion which is long from side to side, wherein the rectangular portion is a basic pattern of the light distribution pattern 29, and the reflecting regions 27, 28 make up for the shortage of an amount of light in the upper and lower positions of the rectangular portion.

12 As clearly can be seen from the above description, a reference curve established on the horizontal surface including the reference axis and a reference curve established on the vertical surface including the reference axis are expressed by the expressions in which a correction term (the polynomial of an even number order) is added to a curve of the second order. A reflecting surface is formed when one reference curve is moved in parallel along the other reference curve so that the reference axis of one curve is located on a horizontal or vertical surface including the reference axis of the other reference curve. When a curve of the second order is deformed by establishing the number of order of the correction term, the luminous intensity distribution in the horizontal or vertical direction can be independently controlled. Therefore, without the help of the lens steps of the front lens, the light distribution control is conducted so that an extreme difference of the luminous intensity can not be caused between the center and the periphery of the light distribution pattern.

The specific profile and construction shown in the above example are only one example provided when the present invention is realized. Therefore, the technical scope of the present invention is not limited to the specific example. For example, in the above example, the central axis of the filament of the electric bulb is disposed in the horizontal direction perpendicular to the primary optical axis of the reflecting section, however, the central axis of the filament may be disposed along the primary optical axis of the reflecting section.

A 1 13

Claims

1. A reflector for a vehicular lamp capable of forming a light distribution pattern diffused in the horizontal direction, wherein a reference curve established on a horizontal surface including a reference axis and a reference curve established on a vertical surf ace including the reference axis are expressed by the following expression:

x= (h 2 /r) / (1 +1 - (1 +k). (h/r) 2) +Am (h n) where 11x11 is a coordinate established on the respective reference axis, 'h" is a coordinate established on an axis perpendicular to the x axis on a horizontal or vertical surf ace including the x axis, Ilrll and 'W' are constants, and ",&M (h n),, is a correction term, which is a polynomial of the n-th order of a positive coefficient relating to "h", wherein 'In" is an even number not less than 4; and a reflecting surface is formed when one reference curve is moved so that the plane in which the moved curve exists remains parallel to the plane in its starting position throughout the movement along the other reference curve so that the reference axis of one curve is located on a horizontal or vertical surface including the reference axis of the other reference curve.

2. A reflector according to claim 1, wherein the reflecting surface of the reflector comprises first and second reflecting regions divided by a vertical surface including a primary optical axis of the reflector, and the reflecting surface of the reflector is used for the reflecting regions, wherein a reference axis of each reflecting region is inclined with respect to the primary optical axis of the reflector.

14

3. A reflector according to claim 2, wherein the reflecting surface of the reflector further comprises an auxiliary reflecting region disposed at the periphery of the first and second reflecting regions.

4. A reflector according to claim 3, wherein the auxiliary reflecting region comprises third and fourth reflecting regions located respectively at a left upper corner and a lef t lower corner of the f irst ref lecting region.

5. A reflector according to claim 4, wherein the third and fourth reflecting regicns are formed as a rotational elliptic surface.

6. A reflector according to any one of the preceding claims, wherein the correction term is a term of low order.

7. A reflector according to any one of claims 1 to 5, wherein the correction term is a term of high order.

8. A reflector according to any one of the preceding claims, wherein degree of reduction of luminous intensity from the centre of projection pattern to the periphery is increased more in a horizontal direction than in a vertical direction.

9. A reflector according to any one of the preceding claims, wherein a lens section of the vehicular lamp is either a plain lens in which lens steps are not formed or a lens approximately the same as a plain lens.

10. A ref lector for a vehicular lamp substantially as described with reference to the accompanying drawings.

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